Reusable balloon system

ABSTRACT

An example reusable high-altitude balloon system includes a control system configured to initiate a termination sequence by separating a payload from an Earth-facing end of the balloon body. Separation of the payload from the balloon body generates a torque that causes the balloon body to invert and release lift gas through a vent duct, initiating a flight termination sequence that facilitates landing of the reusable balloon system without destroying the balloon body.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 62/897,075, titled Reusable Balloon System, and filed onSep. 9, 2019 and also to U.S. Provisional Patent Application No.63/040,378, titled “Reusable Balloon System,” and filed on Jun. 17,2020. Both of these applications are hereby incorporated by referencefor all that they disclose or teach.

BACKGROUND

High-altitude balloons are typically filled with helium, hydrogen,methane, or any mixture of those gasses or other gasses where theresulting mixture is lighter than air. High-altitude balloons may beoutfitted to carry electronics equipment such as transmitters,navigation systems, GPS receivers, and cameras, and are often used inindustries such as weather modeling, aerial imaging, and data collectionfor various types of scientific experimentation. Although earth-orbitingsatellites may be adapted to provide the same science as high-altitudeballoon systems, the comparatively low cost of balloon system equipment,ease of balloon launch, reduced stringency of flight regulations, andtemporary nature of balloon flights make ballooning an appealingalternative.

For safety and environmental protection, some governmental bodies suchas the Federal Aviation Administration (FAA) provide regulationsimposing requirements for reliable termination. To comply with suchregulations, high-altitude balloons are typically equipped with primaryand secondary (e.g., fail-safe) flight termination mechanisms. Currentflight termination mechanisms are designed to initiate descent bydamaging the balloon, such as by tearing a large hole in the body of theballoon. Consequently, most all high-altitude balloons are used a singletime and destroyed during descent. In addition, it is often the casethat a balloon carcass may separate from a payload during a flighttermination sequence and land in a different location. This increasescosts of recovery efforts and also increases risks to the public due tothe existence of multiple objects, rather than a single object, fallingfrom the sky. Still other balloon systems include balloons that are madeof environmentally-adverse materials such as latex or rubber which aremost commonly not recovered. Upon termination such a balloon typicallyexplodes or shreds into multiple pieces, creating substantial litterthat is most typically not recovered. The foregoing limitationsincreases costs and thereby decreases the viability of usinghigh-altitude balloons to perform routine data collection operations.

The weight of a balloon envelope is of great importance to a highaltitude balloon system, as it significantly contributes to the overallweight and size of the system. A heavy system requires more lift gasand, therefore, a larger balloon envelope volume. These considerationshave led to the practice of constructing balloon envelopes from verythin material that are, consequently, typically very fragile. Thisfragility limits the wind velocity that a balloon can be launched inbecause high winds can damage or tear the envelope at launch. The thinfragile material is often not able to survive a descent and recovery,which limits the lifetime of most of these balloon envelopes toone-time-use—a practice that is complementary to the inclusion of theaforementioned balloon termination mechanisms that also destroy theballoon envelope.

SUMMARY

A reusable high-altitude balloon system disclosed herein includes atleast a payload and a control system configured to initiate a flighttermination sequence by separating the payload from a first end of theballoon. Separation of the payload from the first end of the ballooncauses the balloon to invert and release lift gas from within theballoon without destroying the balloon envelope. The lift gas is releasethrough a vent duct also used to arrest the ascent of the balloon.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. These andvarious other features and advantages will be apparent from a reading ofthe following Detailed Description.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1A illustrates the reusable balloon system inflated during flightat the onset of a flight termination sequence above the Earth's surface.

FIG. 1B illustrates the reusable balloon system of FIG. 1A during apayload separation phase of a flight termination sequence.

FIG. 1C illustrates the reusable balloon system of FIG. 1A-1B during aninversion phase of the flight termination sequence.

FIG. 1D illustrates the reusable balloon system of FIG. 1A-1C followinga parachute deployment phase of the flight termination sequence.

FIG. 2 illustrates aspects of another example reusable balloon system.

FIG. 3 illustrates an example payload suitable for implementation in areusable balloon system.

FIG. 4 illustrates further aspects of a reusable balloon system thatincluding a payload that separates from suspension arms during a flighttermination sequence.

FIG. 5 illustrates an example payload that may be designed to detachfrom a balloon body during a flight termination sequence of a reusableballoon system implementing the herein disclosed technology.

FIG. 6 illustrates further details of an exemplary payload detachmentstep during a flight termination sequence for a reusable balloon system.

FIG. 7 illustrates other exemplary aspects of a reusable balloon system.

FIG. 8 illustrates a top-down view of an apex box and clamp ring thatmay form a plug seal that functions as a secondary flight terminationmechanism within a reusable balloon system.

FIG. 9 illustrates a perspective view of an example apex box that may beused in conjunction with a clamp ring to form a plug seal that functionsas a secondary flight termination mechanism within a reusable balloonsystem.

FIG. 10 illustrates a cross-sectional view of another example apex boxthat may be used in conjunction with a clamp ring to form a plug sealthat functions as a secondary flight termination mechanism within areusable balloon system.

FIG. 11 illustrates a top-down view of an example plug seal thatfunctions as a secondary flight termination mechanism within a reusableballoon system.

FIG. 12A illustrates a first exemplary balloon construction phase of aballoon suitable for use within a reusable high altitude balloon system.

FIG. 12B illustrates another exemplary balloon construction phase of areusable balloon following that shown in FIG. 12A.

FIG. 12C illustrates still another exemplary balloon construction phasefollowing that of FIG. 12B.

FIG. 12D illustrates an exemplary balloon construction phase followingthat of 12C.

DETAILED DESCRIPTION

The technology disclosed herein provides high altitude balloon systemfeatures that promote usability and reduce flight recovery costs. Overthe last decade, stronger light-weight materials have becomecommercially available. The herein proposed designs provide forhigh-altitude balloon designs with balloon envelopes constructed fromsuch materials that can perform useful science while greatly improvingthe state of the art via reusability and durability. A balloon made of astrong material can be launched in higher winds than a balloon made of aweak material. It can also be terminated in a non-destructive way thatpreserves the envelope and keeps all parts of the aircraft togetherduring descent minimizing hazards imposed on the National AirspaceSystem (NAS) and to bystanders on the ground. Additionally, strongerballoon envelopes reduce the strain on the world's resources by reducingthe total amount of material that gets discarded every flight, and bykeeping latex, polyethylene and other harmful materials out of naturewhere they are often left as litter.

As discussed above, existing flight termination mechanisms are eitherdesigned to destroy or inadvertently damage the balloon envelope. Topromote reusability of the aforementioned balloon envelopes withincreased durability, the disclosed technology also provides for novelflight termination and landing mechanisms designed to protect theballoon envelope.

According to one implementation, a reusable balloon system includes aflight termination mechanism that initiates a descent and landingsequence without causing damage to the balloon carcass. In the same oranother implementation, the balloon carcass and payload remain attachedto one another throughout the descent and landing sequence such thatthey may be jointly recovered and the entire system reused,substantially without repair, on a subsequent flight.

FIG. 1A-1D illustrate exemplary steps in a flight termination sequenceof a reusable balloon system 100. FIG. 1A illustrates the reusableballoon system 100 during an initial phase of a flight terminationsequence in which a mass is selectively released from a balloon body102. In the examples disclosed herein, the mass that is released is apayload 104. However, the disclosed flight termination sequence could,in other implementations, be initiated by releasing any mass in the samemanner as that described with respect to payload 104. When the balloonbody 102 is filled with a lighter-than-air gas such as hydrogen orhelium, the reusable balloon system 100 is lifted above Earther'ssurface to a target flight altitude, such as to the Earth's lowerstratosphere.

In different implementations, the payload 104 may be equipped withdifferent electronic devices to allow the reusable balloon system 100serve a variety of different purposes. In one implementation, thereusable balloon system 100 is used for weather modeling. Balloons movewith the wind; thus, tracking location of a balloon may facilitatemodeling of wind speed and direction. In such case, the payload 104 mayinclude a GPS receiver in addition to instruments for measuringtemperature and barometric pressure. In another implementation, thereusable balloon system 100 is used for remote sensing, such as aerialimaging, aerial scanning, hyperspectral imaging, thermal imaging,infrared imaging, and/or any other activity for which a high vantagepoint is advantageous to the type of data being collected. Notably, thereusable balloon system 100 may also be well-suited for short durationmissions that are frequently re-launched, such as a data gatheringmission where the amount of data collected by the reusable balloonsystem 100 is too large to downlink, necessitating the landing andrelaunch of the system to download the data and clear memory devices.

A variety of different types of balloon systems may be suitable for theherein disclosed technology. In one implementation, the balloon 102 isdesigned to fly in a configuration known in the industry as a “zeropressure configuration.” A balloon designed to fly in a zero pressureconfiguration expels lift gas (e.g., hydrogen or helium) through a ventupon reaching a target altitude, causing the balloon to stop ascendingand hover for a period of time such as for a few hours or up to a fewdays. The length of time that the balloon 102 hovers at the targetaltitude may be tailored by a flight engineer via design constructs suchas volumetric size, gas type, and other features. To facilitate theventing of lift gas at the target altitude, the balloon 102 may includea vent duct 108 on a first end 106 (e.g., an earth-facing side duringflight) of the balloon 102. The vent duct 108 remains unsealed orloosely sealed, such that building pressure may further open the ventduct to allow lift gas to escape.

In another implementation, the balloon 102 is designed to fly in aconfiguration known as a “super-pressure configuration.” In a superpressure configuration, the balloon 102 is entirely sealed duringflight. As the balloon ascends, pressure inside of the balloon 102increases, therefor increasing the density of the lift gas, and thisbuilding pressure eventually causes the balloon to stop ascending whenthe lift gas is the same density as the surrounding air, at which timeinternal pressure stops building, allowing the balloon to fly for apredefined period of time at a target altitude. In one super-pressureconfiguration that utilizes a flight termination sequence similar tothat shown in FIG. 1A-1D, a vent duct exists on the first end 106 of theballoon 102; however, this duct remains sealed throughout the flight ofthe balloon 102 up until initiation of the flight termination sequence,at which time the vent duct is selectively unsealed to release the liftgas in a manner consistent with that described below.

In either of the above-described configurations, the reusable balloonsystem 100 may include a same or similar a primary flight terminationmechanism that initiates a descent sequence. The primary flighttermination mechanism may be either remotely activated, such as via acommand signal transmitted from the ground or from a satellite, and/orautomatically activated (e.g., preprogrammed) such that the reusableballoon system 100 self-initiates the flight termination sequence. Whenthe primary flight termination mechanism is activated, the payload 104is caused to separate from the first end 106 of the balloon 102. In FIG.1A, the payload 104 is illustrated at a moment just following detachmentfrom the lower end 106 of the balloon body 102.

FIG. 1B illustrates the reusable balloon system 100 of FIG. 1A beginningto rotate following release of the payload 104 during the flighttermination sequence. In one implementation, the payload 104 separatesfrom the first end 106 of the balloon 102 by detaching from suspensionarms 110 that remain attached to the balloon 102. In anotherimplementation, the payload 104 and the suspension arms 110 remainattached to one another but jointly detach from the first end 106 of theballoon 102. In either above-described scenario, the payload 104 dropsaway from the first end 106 of the balloon 102 but remains attached to asecond end 114 of the balloon 102 by a tether 116. The tether 116 maytake on different forms in different implementations, such as that of acord, chain, wire, etc. As the payload 104 swings away from the firstend 106 of the balloon 102, the weight of the payload 104 and the tether116 apply a tension to a tether attachment point 118 on the balloon 102which is, in the illustrated example, located on the second end 114 ofthe balloon that faces away from Earth during flight. This tensioninitiates an inversion of the balloon 102 in which the first end 106 andsecond end 114 flip in position relative to the ground below. Duringthis phase, a parachute 112 drops from a stow position between thepayload 104 and the balloon 102 with tethers attached to the lower end106 of the balloon 102.

FIG. 1C illustrates exemplary inversion of the reusable balloon system100 that results from the rotation described above with respect to FIG.1B. Specifically, the first end 106 (initially facing downward, towardEarth) has rotated 180 degrees and now faces upward (away from Earth.The payload 104 remains attached to the second end 114 of the balloon102 via the tether 116. The balloon 102 remains in this invertedorientation throughout the duration of the flight termination (landingsequence).

In an implementation where the balloon 102 flies in a zero pressureconfiguration (e.g., with an earth-facing vent duct unsealed duringflight), the inversion of the balloon 102 generates internal pressure onthe vent duct 108 on the first end 106, further opening the vent duct108 and thereby allowing the lift gas to rapidly escape. In animplementation where the balloon 102 flies in a super-pressureconfiguration, the flight termination sequence may include an additionalstep that includes releasing a sealed duct on the first end 106 suchthat the vent gas may rapidly escape (as shown) once reaching theillustrated position.

Because the gas in the balloon body 102 is lighter than air andtherefore buoyant, the lighter than air gas vents out of the vent duct108 as shown. In this sense, the vent duct 108 that may vent gas duringascension and/or normal flight of the balloon acts as a release ductduring the flight termination sequence. The venting of the lift gasthrough the vent duct 108 allows the reusable balloon system 100 tobegin to descend.

FIG. 1D illustrates an exemplary parachute deployment phase of a flighttermination sequence that occurs once the balloon 102 has rotated 180degrees responsive to separation of the payload 104 from the second end114. As the lift gas vents through the opening at the first end 106which is now facing away from earth, the parachute 112 opens under forceof the free-falling system, slowing and controlling the descent of theballoon 102 such that the reusable balloon system 100 may land safelywithout damage. As the reusable system 100 descends, the parachute 112inflates, acting as a traditional aerodynamic decelerator. The payload104, balloon 102, and parachute 112 remain attached throughout theremainder of the landing sequence such that all three components may bejointly recovered from a single landing location.

In FIG. 1D, the parachute 112 is shown to be a typical round parachute;however, other implementations may utilize any type of parachute thatslows the descent of the system with respect to the surrounding air. Inat least one implementation, the reusable balloon system 100 utilizes asteerable parachute that can fly horizontally.

FIG. 2 illustrates aspects of another example reusable balloon system200. The system is shown to include at least a payload 202 attached to aballoon body 204. In some implementations, a lower end 216 of theballoon body 204 includes a vent duct. For example, a lower end 216 ofthe balloon body 204 remains open or loosely sealed such that lift gascan escape while the balloon is in flight.

In the illustrated implementation, the lower end 216 of the balloon body204 is shown to have a folded flap configuration 212. For example, thefolded flap configuration 212 may be created by bringing togetherseveral points in the lower end 216 of the balloon body 204 to createflaps (e.g., a flap 214) as shown. In this configuration, each differentone of the flaps may serve as a linkage point that forms a coupling witha corresponding one of multiple suspension arms 216 securing the payload202 to the balloon body 204.

In one implementation where the reusable balloon system 200 flies in azero-pressure configuration, the flaps not used as points of attachmentto the suspension arms 216 are left unsecured such that lift gas canescape through these flaps when the reusable balloon system 200 hasascended to a target altitude. In this configuration, the unsecuredfolds in the lower end 216 of the balloon body 204 serve as theaforementioned vent duct that may vent the lift gas during nominalflight operations as the reusable balloon system 200 ascends to a targetaltitude. This is one example of a zero-pressure configuration. In otherimplementations that also fly the reusable balloon system 200 in azero-pressure configuration, the lower end 216 of the balloon body 204may include any suitable tuck, fold, or releasable seal configurationthat provides for release of the lift gas. During a flight terminationsequence, the balloon body 204 inverts (e.g., as described with respectto FIG. 1A-1D) and the vent duct acts a release duct.

In an implementation where the reusable balloon system 200 is designedto fly in an superpressure configuration, the lower end 216 of theballoon body 204 may be designed to remain sealed throughout nominalflight operations. At the time that the balloon body 204 inverts (e.g.,via a 180 degree rotation) during the flight termination sequence, avent on the lower end 216 of the balloon body 204 is opened to serve asa release duct, as generally described with respect to FIG. 1A-1D.

Referring to View C, the reusable balloon system 200 is shown to furtherinclude a payload 202 secured to the balloon body 204 via suspensionarms 216. A different one of the suspension arms 216 attaches to each ofthe three folds in the folded flap configuration 212.

By example and without limitation, the payload 202 is shown to include acannister 206 supporting a camera 208. For example, the camera 208 maybe designed to facilitate imaging of Earth's surface. According to oneimplementation, the payload 202 includes avionics equipment usable tocontrol a rotation and separation hub (not shown) to cause the cannister206 and camera 208 to rotate relative to suspension arms 210 and theballoon body 204. For example, the rotation of the cannister 206 may berobotically controlled to perform actions in accord with a pre-loaded orread-time command sequence, such to rotate the camera 208 to image largeswaths of the earth while the reusable balloon system 200 moves acrossthe sky.

According to one implementation, the avionics equipment within thecannister 206 also controls a primary flight termination mechanism forthe reusable balloon system 200. For example, the avionics equipmentgenerates a control signal that causes the payload 202 to detach fromthe suspension arms 210 so as to initiate the flight terminationsequence illustrated with respect to FIG. 1A-1D. Although not shown inFIG. 2, the cannister 206 is, in one implementation, secured to an upper(opposite) end of the balloon body 204 via a tether, such as in themanner shown with respect to FIG. 1B.

FIG. 3 illustrates an example payload 300 suitable for implementation ina reusable balloon system. The payload 300 has features the same orsimilar to those shown and described with respect to FIG. 2. The payload302 includes a cannister 304 that includes a camera 306 and otheravionics equipment. Suspension arms 308 attach the payload 302 to aballoon body. In the illustrated implementation, the suspension arms 308include three arms that each include an attachment link (e.g., anattachment link 312) that secures the associated arm to a portion of theballoon body (not shown). Ends of the suspension arms 308 opposite theattachment links 312 connect to a separation and rotation hub 310. Inone implementation, the separation and rotation hub 310 rotates thecannister 304 during nominal flight operations to controllably alter afield-of-view of on-board sensing equipment.

The suspension arms 308 may assume different forms in differentimplementations. When spread out such that the suspension arms 308 havean attachment footprint wider than the separation and rotation hub 310,the side-to-side sway of the cannister 304 is mitigated, stabilizing thepayload 300.

The payload 300 is designed to detach from the balloon body during aflight termination sequence. Although such detachment may be achieved ina variety of different ways, at least one implementation provides fordetachment of the payload 302 from the suspension arms 308 at theseparation and rotation hub 310, as described further with respect toFIG. 4, below.

FIG. 4 illustrates further aspects of a reusable balloon system 400 thatincludes a payload 402 designed to separate from suspension arms 404during a flight termination sequence, such as in the manner thedescribed above with respect to FIG. 1A-1D.

As shown in View B, the payload 402 includes various electronics,sensing, and communication equipment. Among various other on-boardelectronics, the payload 402 includes a controller 412 which may beunderstood as including hardware and/or software. In one implementation,the controller includes memory, computer-executable instructions, andone or more processors (e.g., microprocessors), peripheral interfacecontrollers (“PICs”), application-specific integrated circuits(“ASICs”), systems on chips (“SoCs”), etc. The controller 412 may bepre-loaded with commands sequences and/or configured to receive andexecute real-time commands using a communication system 414.

The controller 412 may be configured to execute firmware sequences toperform various operations in response to execution of pre-loadedcommands (e.g., at designated timestamps) and/or responsive to receiptof commands received in real time, such as from a ground system orsatellite network. In addition to collecting data with remote sensingequipment 420 (e.g., performing science operations), the controller 412also controls detonation of a primary flight termination mechanism 416.

In one implementation, the controller 412 executes the primary flighttermination mechanism 416 responsive to receipt of a real-time commandRF command. In another implementation, the controller 412 executes theprimary flight termination mechanism 416 responsive to satisfaction ofcertain conditions such as upon expiration of a flight timer, at apreselected time, or when a location of the reusable balloon systemsatisfies predefined criteria.

Although the operational principles of the primary flight terminationmechanism 416 may vary from one implementation to another, detonation ofthe primary flight termination mechanism 416 causes the payload 402 todetach from the balloon body (not shown) of the reusable balloon system400. In the specific implementation shown, the separation occurs at ahub including an upper portion 410 a and a lower portion 410 b. The hub(410 a, 410 b) connects suspension arms 418 to the payload 402 and mayalso serve to rotate the payload 402 relative to the suspension arms 418during flight.

It should be understood that the payload separation may be achieved in avariety of ways without departing from the scope of this disclosure.However, in one implementation, the payload is released by a physicallysevering (cutting) a cord, wire, or other line to cause the upperportion 410 a of the hub to separate from the lower portion 410 b of thehub. For example, controller 412 may execute the primary flighttermination mechanism 416 by increasing current flow to a hotwire cutterthat melts a cord (not shown) securing the two portions of the hubtogether.

FIG. 5 illustrates an example payload 500 that may be designed to detachfrom a balloon body during a flight termination sequence of a reusableballoon system implementing the herein disclosed technology. The payload500 includes a cutting assembly 502 that may be controlled to selectablysever a support line (e.g., wire or cord) connecting the payload 500 toa balloon body (not shown). When the cutting assembly 502 is controlledto sever the support line during flight of the reusable balloon system,a lower part of a hub 504 drops away form an upper part (not shown) of ahub that remains attached to the balloon body, at which time the payload500 begins a brief free fall away from the remainder of the system.

In one implementation, the payload 500 remains attached to an upper endof the balloon body even after the above-described separation from thelower end of the balloon body. For example, the payload 500 may beattached to a tether line that wraps around the balloon body andattaches to a top end (e.g., an end facing away from Earth duringflight). Thus, free fall of the payload 500 tensions the tether line andcauses the balloon to invert, such as in the manner described above withrespect to FIG. 1A-1D.

By example and without limitation, the payload 500 is shown to includeother equipment such as a camera 514 with a lens internal to a lens hood510 as well as a battery pack 508 and various avionics equipment 506(e.g., a control board).

FIG. 6 illustrates further details of an exemplary payload detachmentstep during a flight termination sequence for a reusable balloon system600. A payload 604 is selectively released from a lower end 606 of aballoon body 602, such as in a manner consistent with the descriptionsof FIG. 1-6. In one implementation, the payload 604 is, during flight,connected to a parachute cover 610 via an attachment mechanism 614(e.g., a tether). As the payload 604 drops away from suspension arms608, the weight of the payload 604 tensions the attachment mechanism614, pulling the parachute cover 610 off of a parachute (not shown) thatis stowed between the suspension arms 608 and the balloon body 602. Forexample, the parachute and parachute cover 610 are initially stowedtogether in the position 612 a and the removal of the parachute cover610 frees the parachute to hang from this position, as generally shownand described above with respect to FIG. 1B. The parachute cover 610remains attached to the payload 604 and falls away with the payload 604as shown (e.g., at a free-falling position 612 b). This release of theparachute from the stowed position allows for its subsequent deploymentduring the impending free-fall, as shown and described above withrespect to FIG. 1D.

FIG. 7 illustrates other exemplary aspects of a reusable balloon system700. Specifically, aspects of the reusable balloon system 700 describedwith respect to FIG. 7 provide for a secondary flight terminationmechanism that may be used in lieu of a primary flight terminationmechanism such as that described above with respect to FIG. 1A-1D.

The reusable balloon system 700 includes a balloon body 702 with anupper end 704 secured in a manner referred to herein as a plug seal 712.By design, the envelope of the balloon body 702 has an opening at theupper end 704. The aperture of this opening in the balloon body 702 isfitted around an apex box 706 such that an air-tight seal exists betweenthe apex box 706 and the envelope of the balloon body 702. View Billustrates a cross-section of the apex box 706 and the air-tight sealformed between the apex box 706 and the aperture in the balloon body702.

In different implementations, this plug seal 712 may be formed in a sameor similar manner despite variable sizes in the size or shape of theaperture in the balloon envelope. Stated differently, it is not requiredthat the vertical gores (fabric sections, panels) of the balloon body702 have profiles of any particular shape. For example, the balloonprofile could be rectangular, near-rectangular, cylindrical, etc. Theaperture in the upper end 704 of the balloon body 702 could be circular,oval, rectangular, etc.

According to one implementation, the apex box 706 has an o-ring seal 718around its outer perimeter. The plug seal 712 is formed by arrangingfabric of the balloon body 702 around the o-ring seal 718 and lockingthe fabric in position by tightening a clamp ring 714 around the apexbox 706 on an opposite side of the fabric. For example, a turn bucklemay be used to tighten the clamp ring 714 against the o-ring seal 718with the fabric of the balloon body 702 in between, as shown in FIG. 7.

In one example implementation, the plug seal is initially formed whilethe balloon body 702 is inside-out. After the plug seal 712 is formed,the envelope of the balloon body 702 is pulled down (e.g., folded backon itself), turning the balloon body 702 inside-out while pushing theplug seal 712 upward from the bottom of the balloon body 702 to the topof the balloon body 702.

In one implementation, the apex box 706 encases a fail-safe controller722 (e.g., memory, microprocessor, and/or computer-executableinstructions) adapted to execute a secondary flight terminationmechanism 724. The term “secondary flight termination mechanism” is usedinterchangeably herein with the term “fail-safe flight terminationmechanism” to refer to a redundant means of initiating a flighttermination sequence effective to return the reusable balloon system 700to Earth's surface. In general, a “fail-safe” or “secondary” terminationmechanism is a flight termination mechanisms that is not preferred andthat is executed responsive to satisfaction of certain predefinedemergency conditions. For example, the predefined emergency conditionsmay be satisfied when a primary (preferred) flight termination mechanismfails or when conditions are such that the primary flight terminationmechanism becomes unsuitable, such as when a rapid descent is desired(e.g., in a system for which the primary flight termination mechanismsinitiates a comparatively slow descent).

In one implementation, the reusable balloon system 700 includes aprimary flight termination mechanism the same or similar as thatdescribed with respect to FIG. 1A-1D and FIG. 4, whereby detonationtriggers a release of a payload, inversion of the balloon body 702, andventing of lift gas through an opening in the lower end 710 of theballoon body 702 which is rotated to face away from earth during theinversion.

In contrast, selective detonation of the secondary flight terminationmechanism 724 causes a release of the plug seal 712 that separates theapex box 706 from the balloon body 702 such that lift gas can rapidlyescape from the upper end 704 of the balloon body 702. Notably, releaseof the plug seal 712 does not cause an inversion of the balloon body702; rather, this release merely facilitates a rapid release of lift gasthrough the opening that is to remained plugged by the plug seal 712throughout normal flight operations. In instances where the primaryflight termination mechanism is successfully executed, the plug seal 712may remain sealed (as shown) throughout the landing sequence of thereusable balloon system 700.

In different implementations, the secondary flight termination mechanism724 releases the plug seal 712 in different ways. By example and withoutlimitation, the secondary flight termination mechanism 724 of FIG. 7includes a cutting mechanism 720 (e.g., a pyrotechnic cutter) that maybe controlled to sever a cord that is used to tighten the clamp ring 714around the o-ring seal 718 and apex box 706. When the cord is cut, theclamp ring 714 releases its grip on the apex box 706 such that theballoon envelope is freed from the interface between the two, allowingthe apex box 706 and clamp ring 714 to drop down inside of the balloonbody 702.

In different implementations, the fail-safe controller 722 may beadapted to execute the secondary flight termination mechanism 724responsive to satisfaction of different criteria (“emergencyconditions”). In one implementation, the emergency conditions are deemedsatisfied when the reusable balloon system 700 crosses a predefinedgeofence boundary. For example, the fail-safe controller 722 isprogrammed to continuously monitor location data received from a GPSreceiver 726 within the apex box 706. When the location data indicatesthat the reusable balloon system 700 has crossed a predefined geofenceboundary, the fail-safe controller 722 automatically executes thesecondary flight termination mechanism 724. In another implementation,the fail-safe controller 722 is programmed to execute the secondaryflight termination mechanism 724 upon expiration of a timer or at aparticular point in time.

In yet still another implementation, the apex box 706 further includesan RF receiver 730. Upon receipt of a flight termination command at theRF receiver 730, the fail-safe controller 722 executes the secondaryflight termination mechanism 724.

In still another implementation, the apex box 706 transmits GPS locationcollected by the GPS receiver 726 to a ground system controller using RFtransmitter 732. This allows the ground system controller to monitor thelocation of the reusable balloon system 700 and to selectably transmit asecondary flight termination detonation command when a location of thereusable balloon system 700 satisfies certain criteria, such as if theballoon drifts into foreign air space, is approaching a denselypopulated area where landing could potentially create a safety orproperty damage hazard, or otherwise undesirably drifts across a definedgeofence boundary.

Depending upon system design, the apex box 706 may include fewer thanall elements shown in FIG. 7. For example, the apex box 706 may lack theRF receiver 730 and/or the GPS receiver 726. Other aspects of thereusable balloon system 700 not specifically defined with respect toFIG. 7 may be assumed to be the same or similar to those describedelsewhere herein.

FIG. 8 illustrates a top-down view of an apex box 802 and clamp ring 804that may be used to form a plug seal, such as according to the designdiscussed in detail with respect to FIG. 7. In this view, the clamp ring804 is shown relaxed (not tightened) around the apex box 802. To form aplug sea as shown and described with respect to FIG. 6, balloon fabricis routed between the clamp ring 804 and the apex box 802, and the clampring 804 is tightened on the outside of the balloon fabric against theperimeter of the apex box 802. By example and without limitation, theapex box 802 is shown to include a communication system 806 and anantenna 808. In one implementation, the communication system 806 usesthe antenna 808 to transmit location data to a ground station, such asto allow a ground-based human controller to monitor the location of theballoon system. Additionally, the antenna 808 and communication system806 may receive commands sent from the ground to be executed by controlelectronics within the apex box 802. For example, a human ground-basedcontroller may transmit a command that causes on-board controlelectronics to execute a secondary flight termination mechanism thatreleases the plug seal. Characteristics of the apex box 802 and/or theclamp ring 804 that are not described explicitly with respect to FIG. 8may be assumed the same or similar to those discussed elsewhere hereinwith respect to like-named elements.

FIG. 9 illustrates a perspective view of an example apex box 900 thatmay be used in conjunction with a clamp ring (not shown) to form a plugseal that functions as a secondary flight termination mechanism within areusable balloon system, such as according to the design discussed indetail with respect to FIG. 6. The apex box 900 includes a soft sealingsurface 902, such as a rubber o-ring. When the apex box 900 is used toform a plug seal against a balloon envelope, fabric of the balloonenvelope is clamped by the clamp ring against the soft sealing surface902. Characteristics of the apex box 900 that are not describedexplicitly with respect to FIG. 9 may be assumed the same or similar tothose discussed elsewhere herein with respect to like-named elements.

FIG. 10 illustrates a cross-sectional view of another example apex box1000 that may be used in conjunction with a clamp ring (not shown) toform a plug seal that functions as a secondary flight terminationmechanism within a reusable balloon system, such as according to thedesign discussed in detail with respect to FIG. 6. A rubber o-ring 1002wraps around a perimeter of the apex box 1000 and provides a softsealing surface that may be clamped against fabric of a balloonenvelope. A control board 804 is positioned within the apex box 1000. Inone implementation, the control board 804 is coupled to a pyrotechniccutter that severs a cord to release a plug seal, such as in the mannerdescribed above with respect to FIG. 7. Characteristics of the apex box1000 that are not described explicitly with respect to FIG. 10 may beassumed the same or similar to those discussed elsewhere herein withrespect to like-named elements.

FIG. 11 illustrates a top-down view of an example plug seal 1100 thatfunctions as a secondary flight termination mechanism within a reusableballoon system. The plug seal 1100 is formed by an apex box 1102 that ispressed against pleated fabric 1104 of a balloon envelope by a clampring 1106. To better illustrate the folds in the pleated fabric 1104,the clamp ring 1106 is shown in a relaxed position. When the clamp ring1106 is tightened inward toward the center of the apex box 1102 (asindicated by arrows), an air-tight seal is created across the interfacebetween the apex box 1102, pleated fabric 1104, and clamp ring 1106.

In FIG. 11, the pleated fabric 1104 is intended to represent fabric ofthe balloon envelope that has been pleated back and forth around thecircumference of an aperture in the balloon envelope to form acontinuous perimeter of folded pleats. These pleats are “pinched” inplace against the apex box 1102 by the clamp ring. This pleating helpsto ensure that the plug seal 1000 is airtight and symmetrical. Otheraspects of the apex box 1102 or plug seal 1100 may be the same orsimilar to other implementations described herein.

FIG. 12A-12D illustrate various exemplary constructions phases of areusable balloon suitable for use in the implementations disclosedherein. FIG. 12A illustrates a first exemplary balloon constructionphase of a balloon suitable for use within a reusable high altitudeballoon system. In this phase, multiple panels (e.g., a panel 1202) areattached together to make a large rectangle 1204. Although reusableballoon may be variety of shapes and sizes in different implementations,the large rectangle 1204 is, in one implementation ˜35 long by ˜35 feettall. In different implementations, the panels (gores) of the reusableballoon may be made of different materials including without limitationdurable coated fabrics such as reinforced polyethylene, coated ripstopnylon, or polyester, and/or any airtight material such as latex orpolyethylene.

FIG. 12B illustrates another exemplary balloon construction phase of areusable balloon following that shown in FIG. 12A. In this phase, thelarge rectangle 1204 has been transformed into a cylindrical tube 1206by attaching together two opposite sides. In one exemplaryimplementation, the large cylindrical tube 1206 is about 35 feet longand 12 feet in diameter.

FIG. 12C illustrates still another exemplary balloon construction phasefollowing that of FIG. 12B. Here, a first end 1214 of the cylindricaltube 1206 has been uniformly gathered inward such that a number ofpleats 1208 are formed and the aperture is pulled shut to form a sealaround an apex fitting 1210. In one implementation, the pleats 1208 areformed using a jig that includes a number of pins arranged in an annularpattern. For example, the jig may include a first inner circle of pinsinternal to a second outer circle of pins. The fabric of the reusableballoon body is woven back and forth between alternating inner and outerpins of the jig all around, and the pleats created via this techniqueare then clamped into place around the apex fitting 1210 to form a plugseal the same or similar to that shown and described with respect toFIG. 7-11.

FIG. 12D illustrates an exemplary balloon construction phase followingthat of 12C. In this phase, a second end 1216 of the balloon is uniquelyfolded, such as in the manner shown with respect to FIG. 2, to createareas that may serve as linkage points for attaching suspension arms ofa payload-supporting cage. This folding is performed in such a way thatthe second end 1216 the balloon is left partially open so that thereexists a vent 1214 that allows lift gas to escape during ascension ofthe balloon to a target altitude. During a flight termination sequence,the vent 1214 acts as a termination vent to rapidly release the lift gaswhen the reusable balloon is inverted, such as according to the mannershown and described with respect to FIG. 1A-1D.

The above specification, examples, and data provide a completedescription of the structure and use of exemplary embodiments of thedisclosed technology. Since many embodiments of the disclosed technologycan be made without departing from the spirit and scope of the disclosedtechnology, the disclosed technology resides in the claims hereinafterappended. Furthermore, structural features of the different embodimentsmay be combined in yet another embodiment without departing from therecited claims.

What is claimed is:
 1. A reusable balloon system comprising: a balloonwith a first end attached to a mass; and a control system configured toinitiate a termination sequence by separating the mass from the firstend of the balloon, the separation causing the balloon to invert andrelease gas without destroying the balloon; an apex fitting forming aseal with a second end of the balloon opposite the first end, the apexfitting including control circuitry that controllably releases the apexfitting from the second end of the balloon, the seal between the apexfitting and the second end of the balloon including: a plurality ofpleated folds formed in the second end of the balloon around the apexfitting; and a clamp seal that applies a pressure to the pleated foldsaround the apex fitting to form an air-tight seal.
 2. The reusableballoon system of claim 1, wherein the balloon includes at least onevent duct at the first end that releases gas during ascension of theballoon, the inversion of the balloon causing the at least one vent ductto become a release duct and to release the gas during descension of theballoon.
 3. The reusable balloon system of claim 1, further comprising:a tether extending between the mass and a second end of the balloonopposite the first end, the separation of the mass from the first end ofthe balloon tensioning the tether so as to initiate the inversion of theballoon.
 4. The reusable balloon system of claim 1, wherein the apexfitting and the control circuitry operate as a secondary flighttermination mechanism, the secondary flight termination mechanism beingredundant to a primary flight termination mechanism provided by a ventduct that rotates from a downward-facing position to an upward-facingposition responsive to the separation of the mass.
 5. The reusableballoon system of claim 1, wherein the balloon system includes asecondary flight termination mechanism configured to automaticallydeploy when the balloon system crosses a defined geofence boundary, thesecondary flight termination mechanism being redundant to a primaryflight termination mechanism configured to deploy responsive to receiptof an RF command.
 6. The reusable balloon system of claim 1, wherein theseparation of the mass from the first end of the balloon deploys aparachute.
 7. The reusable balloon system of claim 6, wherein the mass,the balloon, and the parachute remain attached to one another until theballoon system has landed.
 8. A method of initiating a terminationsequence for a reusable balloon system comprising: receiving, at controlelectronics on the reusable balloon system, a first command to initiatea primary termination mechanism for a reusable balloon that isin-flight, the first command being executable to controllably separatinga mass from a first end of the reusable balloon responsive to receipt ofthe first command, the separation causing the balloon to invert andrelease gas without destroying the balloon; and receiving, at thecontrol electronics, a second command to initiate a secondarytermination sequence, the second command being executable by circuitryincluded within an apex fitting forming a seal with a second end of thereusable balloon opposite the first end, the seal being formed by aplurality of pleated folds formed in the second end of the reusableballoon that wrap around the apex fitting, the pleated folds beingclamped against the apex fitting by a clamp seal, the secondarytermination mechanism being executable to release the clamp seal to freethe apex fitting from the second end of the reusable balloon.
 9. Themethod of claim 8, wherein the reusable balloon includes at least onevent duct at a first end that releases gas during ascension of theballoon and wherein the inversion of the balloon causes the at least onevent duct to become a release duct that releases the gas duringdescension of the reusable balloon.
 10. The method of claim 8, whereinthe reusable balloon includes a secondary flight termination mechanismconfigured to automatically deploy when the balloon system crosses adefined geofence boundary, the secondary flight termination mechanismbeing redundant to a primary flight termination mechanism configured todeploy responsive to receipt of an RF command.
 11. The method of claim8, wherein the mass remains coupled to a second end of the balloon via atether after separation of the mass, the second end of the reusableballoon being opposite the first end and tensioned by the tether so asto initiate the inversion of the reusable balloon.
 12. The method ofclaim 11, further comprising: deploying a parachute from the first endof the reusable balloon responsive to separation of the mass.
 13. Themethod of claim 12, wherein the mass, the reusable balloon, and theparachute remain attached to one another until the balloon system haslanded.
 14. A balloon system comprising: a reusable balloon attached toa payload at a first end, the reusable balloon including a vent ductthat releases gas during ascension; and a control system configured toinitiate a primary termination sequence by separating the payload fromthe first end of the balloon; and a tether that extends between thepayload and a second end of the reusable balloon, the tether tensioningthe second end of the reusable balloon following payload separation andcausing the reusable balloon to invert such that the vent duct isinverted and acts as a release duct during descension; an apex fittingforming a seal with a second end of the balloon opposite the first end,the apex fitting including control circuitry configured to initiate asecondary termination sequence that that controllably releases the apexfitting from the second end of the balloon, the seal between the apexfitting and the second end of the balloon including: a plurality ofpleated folds formed in the second end of the balloon around the apexfitting; and a clamp seal that applies a pressure to the pleated foldsaround the apex fitting to form an air-tight seal.
 15. The balloonsystem of claim 14, wherein the separation of the payload from the firstend of the balloon deploys a parachute.
 16. The balloon system of claim15, wherein the payload, the reusable balloon, and the parachute remainattached to one another until the balloon system has landed.